My new-to-me 1981 Spirit 28 has a 2QM15 (raw water cooled). Not sure how many hours are on it, since the boat didn't come with an hour meter (PO installed one, about 80 hours currently). Based on boat history (lots of hard storage and marina time), my guess is that the engine has less than 1,500 hours. Visually, it looks virtually new (no rust or visible corrosion anywhere), and it runs very well (although it's a bit hard starting when cold, which seems to be normal for these non-glow plug motors).

Given the high cost of repowering, and its apparent good condition, I'd like to keep this motor running for as long as possible. Based on my internet research, the most common failure modes seem to be corrosion based (exhaust manifold (part not readily available) and mixing elbow), along with head gasket leaks (perhaps also related to corrosion).

A fresh water cooling conversion would appear to reduce the rate of corrosion, but it doesn't appear that conversion kits are offered any longer, so I'd need to engineer my own (not sure the payback would be worth the cost and hassle).

Other than standard routine maintenance, a periodic chemical flush (Rydlyme) appears to be recommended by many. One person suggested an electric pre-oiler (though excessive wear doesn't seem to be a primary failure mode on these engines).

Seakamp Engineering (Bellingham), or AAA Marine in Tacoma can supply nice little heat exchangers that might be worth looking into, but it is a pricey project. You would preserve the current condition of any loss of metals due to corrosion with RWC in play.

Absent the desire or motivation to convert, be sure to keep zincs in good shape (which has hopefully been done up til now)

If you aren't going to use her in the winter you can winterize the engine with antifreeze solution to stop corrosion during the layup period.

Noticed you sail out of Brownsville WA so you probably won't winterize but will be going out all year except for those clear cold days in January when it is 20 degrees and blowing 30 knots. The days following those days will likely show a little drizzle and 50 degrees... underway days.

Noticed you sail out of Brownsville WA so you probably won't winterize but will be going out all year except for those clear cold days in January when it is 20 degrees and blowing 30 knots. The days following those days will likely show a little drizzle and 50 degrees... underway days.

Correct -- sailed her off and on throughout the winter. Better for the engine to get some occasional use, I'm told. (Kind of like us, eh?).

The elbow isn't the real problem as far as longevity of your engine...the real problem will likely be the exhaust manifold. You can buy a new elbow and it won't cost you an arm and a leg. Mine cost about a hundred bucks...if I remember correctly...when I bought it about five years ago.

The exhaust manifold on the other hand is a weak link due to hard scale fouling and relatively thin walls that are subject to corrosion and it has a pretty significant thermal stress due to the temperature difference between the exhaust and cooling. And you can't buy one. If yours fails internally you either have to scavenge one off an old engine if you can find one or have one built. I seem to remember reading about someone having one built a few years ago but I don't remember the details. Would certainly be more expensive than replacing the exhaust elbow.

Another problem area for you if you have the 45 degree elbow rather than the U-shaped elbow may be the transition piece that the elbow screws into on the aft end of the manifold. When my elbow rusted out I was unable to get the elbow out of the transition piece and I had to replace that piece as well. I don't think it is available anymore.

The exhaust manifold on the other hand is a weak link due to hard scale fouling and relatively thin walls that are subject to corrosion ...

My understanding is that periodic flushing with Rydlyme or equivalent will get rid of the scaling, but short of converting to FWC (and replacing the zincs on time), is there anything I can do to keep the corrosion at bay?

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